It is about Yoshimo's heart (and items). I brought it back an was able to give it to a priest in the temple at Waukeen's Promenade. He took it.. and nothing happened (well, he did say there was a chance of Yoshimo being redeemed and all, but nothing more). Is that it?
So, what to do with his katana, then? I still have it. I guess sell or keep it in my usual Athkathla stash (near the dwarven smith at the docks.. in a wooden barrel).
-edit- Oh, right.. Yoshimo. Got it.
I can't be good no more, once like I did before.
I can't be good, baby,
Honey, because the world's gone wrong. ---Bob Dylan, 'World Gone Wrong'